I don’t see the difference between the 2 scripts.

# First script
namespace eval ns1 {
    namespace eval ::ns2 {
        proc name {} {
            puts ok
        }
    }
}
# Second script
namespace eval ns1 {}
namespace eval ns2 {
    proc name {} {
        puts ok
    }
}

In both cases, calling the name procedure is the same writing. My example is very simple, but I thought that my first script protected the ns2 namespace and that I could call the name command only if the ns1 namespace existed.
My apprehension is to have the same namespace ns2 in another package, source… for example.